Abstract: As the test data in the SOC test has the characteristics of large amount of data and its length, put forward a new testmethod for data compression - hybridprefix-run-length encoding.By improving the thought of raditional double run-length coding thought, in each new code added in the group with a special prefix codes to test set of arbitrary length 0 and 1, run simultaneously from longer to variable length coding.By only wreck a code, so as to reduce overall length coding.At the same time decoder scheme based on the finite state machine is presented.The theory analysis and ISCAS89 actual test results show that the coding method has good test compression effect.